How many people can the moon support?

It's the year 3000. After exhausting all the natural resources on the earth, human beings began to emigrate to space. At present, the first space colony has been successfully established on the moon: there is a huge artificial atmosphere above the moon, and hundreds of thousands of people live in the cities below. This cold gray planet has become a new home for mankind.

You may have seen such a beginning in many science fiction novels related to the moon, but today, is living on the moon just a science fiction novel of the earth people? Can it become a reality? If human life on the moon can be realized, how much human life can the moon carry?

How to go to the moon

If you want to live on the moon, the first step is to go to the moon, but this step itself is not easy. So far, only the United States, the Soviet Union and China have successfully landed spacecraft on the moon. Global space agencies and private companies have made more than 30 attempts to land spacecraft on the moon, but more than one-third of the attempts ended in failure. These failed landers either hit the moon or "lost contact" during the landing. Only the United States has achieved limited success in manned landing on the moon.

So what should I do to successfully land on the moon? First, we must choose the path to the moon. If you want to "take a shortcut" and reach the moon as soon as possible, you must prepare an adequate transportation budget, such as the United States. As early as 50 years ago, the Apollo 1 1 spacecraft with powerful engine and sufficient fuel was built at a cost of billions of dollars. It started from the earth, went straight to the moon, and arrived at the moon three days later.

But if there is not enough transportation cost, we must be prepared to "go far". In the Indian "Moon Ship 2" moon landing plan from 2065438 to late July 2009, the spacecraft chose a circuitous route to save costs. It has to fly around the earth several times, slowly improve its orbit and speed, and fly to the moon by inertia. The lander vikram took more than a month to reach the landing site of the moon, but the advantage of saving money is obvious. India spent less than $200 million, less than one-fifth of that of the United States.

After choosing the right path for the spacecraft, it is also important to find the right landing site and keep in touch and accept the command. Just as the plane needs to contact the air traffic control department to determine the landing direction and runway before landing, the lunar lander also needs to receive data and instructions from the earth. Vikram, a lunar probe launched by India, lost contact with its home base, the Indian Space Research Organization, only 2 kilometers away from the surface of the moon, and finally landed on the moon independently. It is still "uncertain".

Landing on the moon is so complicated and expensive. Do we have a better solution?

Compared with a spaceship that costs hundreds of millions of dollars and can't carry many people, the space elevator will be a more economical mode of transportation. Salamanca Riba, a professor of engineering at the University of Maryland in the United States, put forward the idea of a space elevator with carbon nanotubes. In order to reach the moon, we need hundreds of thousands of kilometers of cables, which are made of very strong and very light carbon nanotubes. It is estimated that the cost of going into space by space elevator is less than one tenth of that by spaceship.

However, because the carbon nanotubes we can make in the laboratory are only a few centimeters long, the idea of making space elevators with carbon nanotubes is still far away. It seems that at present, we may still rely on spacecraft to land on the moon.

Dietary problems on the moon

When you come to the moon, you have to solve the problem of how to survive. Oxygen, water and food are all urgent problems to be solved, and scientists have also given some solutions to these problems.

We know that there is no oxygen in the atmosphere of the moon, but there is a lot of oxygen on the moon. The surface of the moon is covered with a layer of fine particles, which we call lunar soil. It consists of metal oxides such as iron oxide, silicon oxide and aluminum oxide, and contains 40% and 45% oxygen. If we can decompose these oxides, we can get enough oxygen.

Research teams from the University of Glasgow and the Kennedy Space Center of NASA both used the same molten salt electrolysis method to obtain oxygen from lunar soil. The researchers will heat the lunar soil above 1649, and then electrify the lunar soil melted at high temperature to decompose it and obtain oxygen.

There is no need to worry about water. First, scientists found that there is a lot of water inside the moon. There are three main forms of water on the moon, one is crystal water combined with minerals, and the other is ice in the Antarctic region of the moon, both of which need to be melted at high temperature after mining before they can be used; The last kind of moisture was inferred by the calculation of planetary scientist Medy Banner of NASA. He found that whenever a meteor hits the moon, the water content in the outer atmosphere of the moon is always extremely high. From October 20 13 to April 20 14, there were 29 meteor showers on the moon, all of which detected water. According to this, he thinks there is some water under the shallow surface of the moon. When the meteor hits the moon, it destroys the soil layer on the surface of the moon, and the water molecules buried below are released, so there is water in the outer atmosphere of the moon. If the later detection results are true, then these shallow groundwater are easier to collect and apply than the former two.

Secondly, we can recycle water. At present, it is very common for astronauts to drink their own purified shower water, urine and sweat on the International Space Station. According to NASA, an average astronaut needs to drink 730 liters of recycled drinking water during a one-year mission. After recovery, deodorization, distillation, sterilization and other steps, the recovered water is clean enough for drinking. On the moon, this technology can also be used to build a closed-loop water system for residents and exploit the shallow groundwater on the moon, which can be recycled and reused for many times after the first use.

The problem of drinking water has been solved, and diet also needs to be taken into account. In recent years, there are more and more kinds of space food for astronauts, from a dozen to hundreds. Recently, they also ate their own vegetables grown in the space station.

In 20 14, NASA planted lettuce on the international space station for the first time. They irradiated lettuce with light. Studies have shown that this can make lettuce yield higher. In space, lettuce grows very fast and can be harvested in 28 days. Three astronauts ate this kind of lettuce in space. They said it tasted as fresh and delicious as the lettuce grown on the earth.

In 20 19, Chinese astronauts placed a "small garden" on the moon. This project is called "Biological Experiment Popular Science Load" and is designed by researchers of Chongqing University. "Small Garden" is a round barrel made of aluminum alloy, which is similar to a milk powder jar. Cotton seeds, rape seeds, potato seeds, Arabidopsis seeds, yeast, fruit flies, nutrient solution, camera and information transmission system will be placed inside.

In the imagination of scientists, the "small garden" is a mini biosphere. It is equipped with an intelligent air conditioner that can automatically adjust the temperature, which can keep the temperature of130 for a long time, and introduce the light on the surface of the moon through the light pipe on the surface, which is convenient for plants to carry out photosynthesis and release oxygen and organic matter. At the same time, the carbon dioxide and feces produced during the growth of fruit flies after hatching are beneficial to the growth of plants, thus maintaining the micro-ecological cycle in the "small garden".

The "small garden" was taken to the moon, and in the photos sent back nine days later, cotton seeds have sprouted and grown tender leaves. Unfortunately, the moon soon entered the night time of 14 days, and the temperature conditions were even worse, and other seeds did not germinate.

The "small garden" project is a preliminary attempt to cultivate agriculture on the moon. The failure of this attempt once again reminds us of the difference between the moon and the earth. If no new crops can be found to adapt to the lunar environment, it may be an expedient measure to build a lunar greenhouse buried underground. Gene giacomelli, a biology professor at Arizona State University, came up with this idea. Researchers plan to bury it under the surface of the moon to avoid damage caused by cosmic rays and solar flares. The computer controls the temperature inside the greenhouse, and plants can get carbon dioxide from the exhaust gas exhaled by astronauts. As for the water needed by plants, it can be combined with the recovery and purification system of human body. Plants absorb water from the surface. We collect the evaporated water from the plants above the greenhouse, purify it for human use, and collect the sewage and return it to the plants.

Does the "Moon Greenhouse" project sound similar to "Biosphere 2"? Two "Biosphere 2" experiments ended in failure. Is there any possibility of success in the "moon greenhouse"? If we summarize the reasons for the failure of Biosphere 2, then the most important thing is that Biosphere 2 introduced a limited number of species in a limited area, and then cut off contact with the outside world, hoping to achieve complete self-sufficiency, but eventually the ecosystem was unbalanced and collapsed, and the plan failed. This reminds us that the balance of environmental conditions such as oxygen, humidity and temperature in the greenhouse cannot be maintained only by the self-circulation of organisms in the greenhouse.

So what should we do? We need to replenish oxygen and water to the greenhouse regularly to maintain the circulation. However, oxygen and water on the moon are hard to get, which requires a lot of energy. Fortunately, the moon has abundant and economical energy, that is, helium -3, which is as much as 2 million times that of the earth and can be used by human beings for tens of thousands of years. Helium -3 is a gas composed of helium isotopes. Researchers at the Massachusetts Institute of Technology have found that it is more efficient and feasible to use helium -3 as the fuel for nuclear fusion. Relying on these energy sources, we can carry out continuous chemical reactions and obtain the supplement of living substances.

Other problems still exist.

However, even if the most basic problems of food, clothing, housing and transportation can be solved, there are still some problems for the moon to become the first space colony of the earth people.

First of all, natural disasters on the moon are no less than those on the earth, and they are even more unpredictable. As we know, a big difference between the moon and the earth is that it does not have a magnetic field around the earth, which will do great harm to people. For example, the "sunburn" recently photographed by NASA's Artemis lunar probe is caused by the fact that the moon has no magnetic field to resist the solar wind.

What is sunburn? It turns out that the sun keeps releasing high-speed charged particles into space, which is the solar wind. When these charged particles meet the earth's magnetic field, their direction will be deflected, which will not cause harm to the earth and its creatures. But unlike the moon, some rocks on the surface of the moon contain metallic iron, which makes these rocks magnetic and can generate a small magnetic field. Therefore, when the solar wind strikes, the place with magnetic field avoids the invasion of high-energy particles, while the place without magnetic field reacts with high-energy particles and the surface darkens. In this way, the surface of the moon becomes a pitted surface with alternating bright spots and dark spots, which are the result of sunburn by the sun.

If we live on the moon in the future, we must always be ready to "protect ourselves from the sun". If we can't create a magnetic field, we will have to stay at home every day.

Under the influence of the solar wind, the moon soil with great power can not be underestimated. The lunar soil will be charged under the baptism of the solar wind. Floating in the air for a long time after being charged, it is easy to attach to people, inducing symptoms similar to pollen allergy, damaging human DNA and increasing the risk of cancer.

In addition to natural disasters, the interior of the moon is not calm. Recently, German scientists speculated that earthquakes are likely to occur frequently on the moon. Because a long time ago, scientists often found flashes on the moon, but they didn't find the reason. Until recently, researchers at the University of Wü rzburg, Germany, found that when there is an earthquake on the moon, flashing phenomena are observed, sometimes lasting for several hours. They think this is because during the earthquake, gases under the surface of the moon escape into the atmosphere, and they will reflect sunlight, so the moon will flicker. The moon often flashes, indicating that earthquakes may occur frequently. If that's the case, how can the moon that earthquakes from time to time make people settle down?

In addition, the time difference and temperature difference between the moon and the earth also have some influence. The moon also has revolution and rotation, but the scene of the sun rising and setting on the moon is different from that on the earth. The rotation speed of the moon is very slow, and a day and night on the moon is equivalent to 27.32 days on the earth.

Because there is no scattering on the moon, the sunlight in the daytime is 100 times brighter than that on the earth, and the temperature is much higher than that on the earth, which can be as high as 120, and in the dark time of about two weeks, the temperature will drop to about-200. How can I spend such a long and difficult day and night?

If we can overcome the above problems, we can now consider how many people the moon can hold. If we only consider the geographical area and resource conditions of the moon, theoretically speaking, the moon with a land area of about 15.9% of the total land area of the earth can accommodate billions of people. But if so many people really flood into the moon, its fragile habitat may soon collapse in people's plunder.

So the question of how many people the moon can hold depends on our scientific and technological development and carrying capacity; It also depends on the level of development and management of the moon.